How can I connect multiple ADT7310 or ADT7320 temperature sensors to the same SPI bus?
To connect multiple ADT7310/ADT7320 devices to the same SPI bus, connect the SCLK, DIN and DOUT of each device directly to the bus and use the /CS pins of each device to select the active device by pulling its /CS pin low.
Do not daisy chain the devices! (i.e. connect DOUTt of one device to the DIN of another device).
Is there a design limitation as to why we cannot daisy chain the adt7320??? Seems counter intuitive to have an SPI interface and not be able to daisy chain multiple devices.
If you look at the Serial Interface section, it's described how the SPI interface works. When you clock in, through the DIN line, a certain code, you will get the corresponding register value on the DOUT line. There is no option to clock in one sensor's output to the following sensor's input.
However, if you want to connect several sensors to the same bus, you can share DIN, DOUT, SCLK among all of them, and use a /CS line for each sensor. This way, depending on which /CS line is pulled low, its corresponding sensor will be read or writen through the DIN,DOUT lines.
Thanks for the quick response Lluis.
I have a design requirement where we have been asked to connect multiple adt7320 devices. Ranging from a minimum of 5, all the way to 100 for one configuration. One hundred /CS lines is going to be a challenge. We have several scenarios to work with. I may update the forum when we have one working array of 100 devices...
Cheers, Antonio Benci.
You may need then to mux your /CS lines from the controller into multiple /CS lines of each of the sensor, if that's an option.
May I correct you on a point of error in your reply. DIN, and SCLK can be shared, DOUT CANNOT be shared as it is NOT a tristate capable pin. It would seem that I will need an individual /CS and DOUT connection for each device. The current data sheet does not indicate any tristate capability for this device and in testing with 5 devices it was found that sharing the DOUT pin does not work, the out puts from the device will clash.
The inclusion of a TI tiny logic tristate buffer corrects the DOUT issue. It would be helpful is such information is included in the data sheet.
Regards, Antonio Benci.
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